The I-WLAN (Interworking Wireless Local Area Network) is a WLAN network interacting with the 3GPP (the 3rd Generation Partnership Project) network. The I-WLAN mainly comprises a WAN (WLAN Access Network), a WAG (WLAN Access Gateway), a PDG (Packet Data Gateway) and other supporting nodes. The purpose for interacting is to enable the cooperation between the WLAN access technology and the facilities of the 3GPP core network, so that the WLAN subscriber can access the 3GPP packet service through the WLAN access network.
The GPRS (General Packet Radio Service) access network comprises a 3GPP wireless access network (GSM EDGE Radio Access Network/UMTS Terrestrial Radio Access Network, GERAN/UTRAN for short), an SGSN (Serving GPRS Support Node), a GGSN (Gateway GPRS Support Node) and other support nodes.
A mobile subscriber having the access capability for the I-WLAN and GPRS Access Network requires to keep service continuity when switching between the two access networks. The 3GPP Standard Organization has determined to employ DSMIPv6 (Dual-Stack Mobile Internet Protocol version 6) as the solution to keep service continuity. The solution enables the mobile subscriber to keep IP address unchanged after the mobile subscriber switches between the I-WLAN and GPRS Access Network, so as to realize the continuity of the service.
FIG. 1 is the architecture diagram of the mobility solution (I-WLAN Mobility) between the I-WLAN network and 3GPP Network.
As shown in FIG. 1, a UE (User Equipment) can access the I-WLAN network and 3GPP network. Both the GGSN and PDG can be considered to be ARs (Access Routers). An HA (Home Agent) and corresponding 3 interfaces, i.e., H1 (between the HA and UE), H2 (between the HA and 3GPP AAA Server), and H3 (between the HA and AR) are added between the above mentioned I-WLAN network and 3GPP network.
3GPP EPS (Evolved Packet System) is consisted of an evolved UTRAN (Evolved Universal Terrestrial Radio Access Network, E-UTRAN for short), an S-GW (Serving Gateway), a PDN GW (Packet Data Network Gateway, PDN GW or P-GW for short) and other supporting nodes. The S-GW is an access gateway device connected to the E-UTRAN, which forwards data between the E-UTRAN and PDN GW, and is in charge of buffering the paging waiting data; the P-GW is a border gateway between the EPS and the PDN (Packet Data Network) network, and is in charge of the functions, such as the accessing of the PDN and the data forwarding between the EPS and the PDN.
FIG. 2 is the architecture diagram for a non-3GPP network accessing the EPS network.
As shown in FIG. 2, the EPS supports the interaction with a non-3GPP network. The P-GW functions as an anchor during the switch between the 3GPP network and the non-3GPP network. The subscriber uses an S2c interface when accessing the EPS network using the terminal-based mobile IP protocol, wherein the S2c interface is an interface between the UE and the P-GW.
The mobile IP protocol is a network layer scheme for providing mobile function on Internet, so that the node can not interrupt the ongoing communication when switching a link Especially, the mobile IP provides an IP routing mechanism, which enables the mobile node to be visited through its home address when it accesses a foreign link.
Some important special terms related to the mobile IP will be explained hereafter.
Mobile node is a node in the mobile IP which can move from one connection point to another connection point of a link and still can be visited through its home address.
Home agent is a router in the home link of the mobile node. When the mobile node leaves the home link, it can intercept, on its home link, the data package whose destination address is the home address of the mobile node, and forward the data package to the care of address registered by the mobile node via a tunnel.
Home Address (HoA for short) refers to a permanent IP address assigned to the mobile node and belongs to the home link of the mobile node. A standard IP routing mechanism can transmit the packet to be sent to the home address of the mobile node to another home link. The Home Network Prefix is (HNP for short) is the prefix of the IPv6 home address. In present Specification, the HoA allocated by the HA can be the HNP.
Care of Address (CoA for short) refers to an IP address acquired by the mobile node at the time of visiting a foreign link. The sub-network prefix of such an IP address is a foreign sub-network prefix.
Home Link is a network corresponding to the home sub-network prefix of the mobile node.
Foreign Link is any link other than the home link.
Binding refers to the correlation between the care of address and the home address of the mobile node.
When a UE, as a mobile node, accesses the I-WLAN Mobility system or EPS network, the mobile IP protocol (DSMIPv6) is used to keep the IP address of the subscriber unchanged, so as to maintain the continuity of the subscriber service When the UE accesses the I-WLAN Mobility system and EPS network, the network is composed of an access router (AR) and a home agent (HA). The GGSN, PDG and P-GW, as the access routers of the subscriber, assign an access network address to the UE, wherein the address is used as the CoA when the UE uses mobile service, When the UE uses mobile service, the UE initiates IKEv2 (Internet Key Exchange version 2) to establish security association with the HA, and during the IKEv2, the HA will assign an IP address (HoA) for the UE and send this address to the UE.
The UE does not utilize the mobile IP protocol when accessing the Home Link, and does not bind the HoA and the CoA at the HA. The I-WLAN Mobility system can configure the GPRS or I-WLAN as the home link of the UE; the home link of the UE can be configured as the EPS access network (E-UTRAN) in the EPS network. When the UE accesses the home link configured above, there are three methods to enable the UE to discover whether the current access link is the home link in the prior art.
Method 1, information, such as home agent address, home address of the UE is statically configured in the UE, the UE detects the router broadcast on the current IP link, if a link address prefix in the broadcast content is consistent with a prefix of its home address, then it is considered that the home link is accessed;
Method 2, the UE link layer detects the current access technology, and determines whether the current access network is the home link according to the previously configured information and informs the IP layer;
Method 3, when the UE receives the current access information, the subscriber selects whether the current access link is the home link.
Method 1 and Method 2 require to configure corresponding information in the UE and thus reduces the flexibility of the use; Method 3 requires the participation of the subscriber and thus increases the complexity and affects subscriber experience.